Project Summary/Abstract: Owing to the successful use of engineered microbial opsins to remotely control neuronal excitability at high spatiotemporal resolution, considerable new insights into the causal relationship between circuit activity and neuropsychiatric diseases have been obtained through optogenetic approaches. Existing optogenetic tools are primarily designed to manipulate the flow of ions, such as sodium, potassium and chloride, that support an electrogenic role in the brain of mammals. By contrast, calcium ion passing through voltage gated calcium (CaV) channels not only alters membrane potential but also functions as an indispensable messenger to regulate neuronal gene expression, synaptic transmission, neurite outgrowth and memory formation. CaV channels are also essential for cardiac and smooth contractility. CaV channels serve as emerging and attractive therapeutic targets for neuropsychiatric and cardiovascular diseases. However, noninvasive tools to directly and selectively photo-modulate the flow of calcium ion in neurons and cardiomyocytes are still limited. Another technical roadblock that faces the current in vivo optogenetics and optical neuromodulation is the inability of most existing tools to stimulate deep and wide within the brain without the use of invasive indwelling fiber optic probes. To tackle these two technical challenges, we propose to optically inhibit CaV channel activity by engineering light sensitivities into key CaV negative regulators, and in parallel, to develop bio-compatible nano-antennae-upconversion nanoparticles (UCNPs) as a ?cordless? optogenetic platform to capture and convert low power, tissue-penetrant, near infrared radiation (NIR) into blue light. This nanoantenna will act as a light-delivery transducer to modulate voltage-gated calcium channels, as well as calcium-dependent activities in excitable tissues, with precise spatiotemporal control. We propose two specific aims to advance our platform to excitable cells by using neuronal cells as proof-of-concept. In Aim 1, we will develop new optogenetic tools to photo-control CaV channel function, and characterize the capacity of our first-generation UCNPs to act as ?nanoantenna?. In Aim 2, we will develop next generation UCNPs with high photoconversion efficiencies and enhanced biocompatibility. We anticipate that our NIR light-stimulable optogenetic platform will enable remote and noninvasive control of cell activities in excitable tissues, and permit modulation of their intricate inter- cellular interactions under both physiological and pathological conditions at large scale. Given the wide distribution and close involvement of CaV channels in multiple diseases, the techniques and tools that we develop can be broadly extended to interrogate other types of tissues across multiple systems. In summary, the proposed early-stage, cordless optogenetic technology is anticipated to overcome many of the limitations of current fiber optics-based optogenetic approaches, and will enable new and broad applications in both biomedical research and human health.